Analysis of oil and gas flow characteristics in the reservoir with the elastic outer boundary

In the light of the idealization of the outer boundary conditions (infinite, constant pressure and closed) of the conventional homogeneous reservoir model, the paper introduces the elastic outer boundary conditions and establishes the percolation model of homogeneous reservoir. By combining Laplace transforms with the Similarly Construction Method, the solutions of the percolation model of homogeneous reservoir can be obtained in Laplace space. The solutions are inverted into real space with the Stehfest numerical inversion method. In addition, the characteristic curves are drawn, and the impacts of the variation of the main parameters on the curves are analyzed. The results show that the conventional three kinds of outer boundary conditions are actually three special cases of elastic outer boundary. The pressure curve under the elastic outer boundary is between the pressure curve of the constant pressure outer boundary and the closed outer boundary, and the curves above exhibit affine similarities. In this paper, the elastic outer boundary condition is introduced not only to enlarge the range of data interpretation, but also to reflect the real situation of the outer boundary of oil and gas reservoir (Strict closed and constant pressure boundaries rarely exist in real reservoirs). The similarly construction theory greatly simplifies the complicated process of solving the model, which will have a profound influence on the development of the well test analysis software in the future.